U.S. patent application number 11/289214 was filed with the patent office on 2007-05-31 for turbocharger with sliding piston assembly.
Invention is credited to Alain R. Lombard, Marylene Ruffinoni, Laurent Vautier.
Application Number | 20070122268 11/289214 |
Document ID | / |
Family ID | 37596155 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070122268 |
Kind Code |
A1 |
Lombard; Alain R. ; et
al. |
May 31, 2007 |
Turbocharger with sliding piston assembly
Abstract
A turbocharger having a sliding piston assembly comprising a
tubular piston disposed in the bore of the turbine housing such
that the piston is axially slidable relative to the turbine
housing. The piston assembly further comprises a tubular carrier
inserted axially into the bore of the turbine housing surrounding
the piston and fixed against axial movement relative to the turbine
housing, a radially outer surface of the carrier engaging an inner
surface of the bore and a radially inner surface of the carrier
being slidably engaged by a radially outer surface of the piston.
The carrier defines an axial split extending a length of the
carrier, and the carrier is resiliently flexible. Accordingly, the
axial split allows the carrier to expand and contract in
diameter.
Inventors: |
Lombard; Alain R.; (Uxegney,
FR) ; Ruffinoni; Marylene; (Les Forges, FR) ;
Vautier; Laurent; (Tendon, FR) |
Correspondence
Address: |
HONEYWELL TURBO TECHNOLOGIES
23326 HAWTHORNE BOULEVARD, SUITE #200
TORRANCE
CA
90505
US
|
Family ID: |
37596155 |
Appl. No.: |
11/289214 |
Filed: |
November 29, 2005 |
Current U.S.
Class: |
415/158 |
Current CPC
Class: |
F05D 2220/40 20130101;
F01D 17/167 20130101; F05D 2240/10 20130101; F01D 17/143 20130101;
F05D 2230/642 20130101 |
Class at
Publication: |
415/158 |
International
Class: |
F04D 15/00 20060101
F04D015/00 |
Claims
1. A turbocharger comprising: a center housing containing a bearing
assembly and a rotary shaft mounted in the bearing assembly; a
compressor wheel affixed to one end of the shaft; a turbine wheel
affixed to an opposite end of the shaft and disposed in an axial
bore of a turbine housing coupled to an opposite side of the center
housing, the turbine housing defining a chamber surrounding the
turbine wheel for receiving exhaust gas to be directed into the
turbine wheel, and defining a nozzle leading from the chamber to
the turbine wheel; and a sliding piston assembly comprising: a
tubular piston disposed in the bore of the turbine housing such
that the piston is axially slidable relative to the turbine housing
between a closed position and an open position, the piston in the
closed position substantially blocking exhaust gas from passing
through the nozzle to the turbine wheel, the piston progressively
unblocking the nozzle as the piston travels toward the open
position; and a tubular carrier inserted axially into the bore of
the turbine housing surrounding the piston and fixed against axial
movement relative to the turbine housing, a radially outer surface
of the carrier engaging an inner surface of the bore and a radially
inner surface of the carrier being slidably engaged by a radially
outer surface of the piston, the carrier defining an axial split
extending a length of the carrier, and the carrier being
resiliently flexible, such that the axial split allows the carrier
to expand and contract in diameter.
2. The turbocharger of claim 1, wherein the inner surface of the
bore of the turbine housing defines a step surface and the carrier
defines a radially outwardly projecting protuberance that engages
the step surface for fixing the carrier against axial movement and
for providing sealing between the carrier and turbine housing.
3. The turbocharger of claim 2, further comprising a snap ring
engaging a groove in the turbine housing, the snap ring engaging
the carrier and pressing the carrier against the step surface.
4. The turbocharger of claim 1, wherein the length of the carrier
is approximately equal to that of the piston.
5. The turbocharger of claim 1, wherein the carrier defines a
plurality of apertures extending through a side wall of the carrier
and circumferentially spaced about the carrier, the apertures being
axially elongated.
6. The turbocharger of claim 5, further comprising a piston
actuating linkage disposed adjacent the outer surface of the
carrier and having piston-engaging members that extend through the
apertures in the carrier and connect to the piston.
7. The turbocharger of claim 6, wherein the piston actuating
linkage comprises a fork-shaped swing arm, the piston-engaging
members comprising two arms of the swing arm, the arms having
distal ends that extend through the apertures in the carrier and
connect to the piston at diametrically opposite locations thereof,
the swing arm being pivotable about a transverse axis so as to
cause the arms to axially move the piston within the carrier.
8. The turbocharger of claim 7, wherein an axially intermediate
portion of the bore of the turbine housing has an enlarged diameter
for accommodating the swing arm.
9. The turbocharger of claim 1, wherein the bore of the turbine
housing and the carrier are structured and arranged such that the
carrier is insertable axially into the bore from one end of the
bore.
10. A sliding piston assembly for a turbine of a turbocharger, the
turbine comprising a turbine housing defining an axial bore in
which a turbine wheel is disposed and defining a chamber
surrounding the turbine wheel for receiving exhaust gas to be
directed into the turbine wheel, and defining a nozzle leading from
the chamber to the turbine wheel, the sliding piston assembly
comprising: a tubular piston structured and arranged to be disposed
in the bore of the turbine housing such that the piston is axially
slidable relative to the turbine housing between a closed position
and an open position, the piston in the closed position
substantially blocking exhaust gas from passing through the nozzle
to the turbine wheel, the piston progressively unblocking the
nozzle as the piston travels toward the open position; and a
tubular carrier structured and arranged to be inserted axially into
the bore of the turbine housing surrounding the piston and fixed
against axial movement relative to the turbine housing, the carrier
comprising a radially outer surface for engaging an inner surface
of the bore and a radially inner surface of the carrier slidably
engaged by a radially outer surface of the piston, the carrier
defining an axial split extending a length of the carrier, and the
carrier being resiliently flexible, such that the axial split
allows the carrier to expand and contract in diameter.
11. The sliding piston assembly of claim 10, wherein the carrier
defines a radially outwardly projecting protuberance for engaging a
step surface of the turbine housing for fixing the carrier against
axial movement and for providing sealing between the carrier and
turbine housing.
12. The sliding piston assembly of claim 10, wherein the length of
the carrier is approximately equal to that of the piston.
13. The sliding piston assembly of claim 10, wherein the carrier
defines a plurality of apertures extending through a side wall of
the carrier and circumferentially spaced about the carrier, the
apertures being axially elongated.
14. The sliding piston assembly of claim 13, further comprising a
piston actuating linkage disposed adjacent the outer surface of the
carrier and having piston-engaging members that extend through the
apertures in the carrier and connect to the piston.
15. The sliding piston assembly of claim 14, wherein the piston
actuating linkage comprises a fork-shaped swing arm, the
piston-engaging members comprising two arms of the swing arm, the
arms having distal ends that extend through the apertures in the
carrier and connect to the piston at diametrically opposite
locations thereof, the swing arm being pivotable about a transverse
axis so as to cause the arms to axially move the piston within the
carrier.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to turbochargers,
and relates more particularly to exhaust gas-driven turbochargers
having an axially sliding piston for varying the size of a nozzle
opening leading into the turbine wheel of the turbine so as to
regulate flow through the turbine.
[0002] Regulation of the exhaust gas flow through the turbine of an
exhaust gas-driven turbocharger provides known operational
advantages in terms of improved ability to control the amount of
boost delivered by the turbocharger to the associated internal
combustion engine. The regulation of exhaust gas flow is
accomplished by incorporating variable geometry into the nozzle
that leads into the turbine wheel. By varying the size of the
nozzle flow area, the flow into the turbine wheel can be regulated,
thereby regulating the overall boost provided by the turbocharger's
compressor.
[0003] Variable-geometry nozzles for turbochargers generally fall
into two main categories: variable-vane nozzles, and sliding-piston
nozzles. Vanes are often included in the turbine nozzle for
directing the exhaust gas into the turbine in an advantageous
direction. Typically a row of circumferentially spaced vanes extend
axially across the nozzle. Exhaust gas from a chamber surrounding
the turbine wheel flows generally radially inwardly through
passages between the vanes, and the vanes turn the flow to direct
the flow in a desired direction into the turbine wheel. In a
variable-vane nozzle, the vanes are rotatable about their axes to
vary the angle at which the vanes are set, thereby varying the flow
area of the passages between the vanes.
[0004] In the sliding-piston type of nozzle, the nozzle may also
include vanes, but the vanes are fixed in position. Variation of
the nozzle flow area is accomplished by an axially sliding piston
that slides in a bore in the turbine housing. The piston is tubular
and is located just radially inwardly of the nozzle. Axial movement
of the piston is effective to vary the axial extent of the nozzle
opening leading into the turbine wheel. When vanes are included in
the nozzle, the piston can slide adjacent to radially inner (i.e.,
trailing) edges of the vanes; alternatively, the piston and vanes
can overlap in the radial direction and the piston can include
slots for receiving at least a portion of the vanes as the piston
is slid axially to adjust the nozzle opening.
[0005] The sliding-piston type of variable nozzle offers the
advantage of being mechanically simpler than the variable-vane
nozzle. Nevertheless, other drawbacks have generally been
associated with sliding-piston type variable nozzles. The piston
must be somewhat smaller in diameter than the inner diameter of the
turbine housing bore to ensure that the piston can freely slide
without binding. As a result, a potential leakage pathway exists
through the inevitable gap between the piston and bore. Leakage of
exhaust gas through this pathway reduces turbine performance.
[0006] Furthermore, dimensional changes in the turbine housing
and/or piston as a result of thermal expansion and contraction can
lead to growth of the gap and hence increased leakage. Typically
the piston is of a different material from that of the turbine
housing, and the two materials have different coefficients of
thermal expansion. As a result, it is generally necessary to design
the piston-to-housing clearance on the high side at low
temperatures to avoid binding of the piston at high temperatures,
or vice versa, depending on the relative coefficients. Accordingly,
during some operating conditions the gap between the piston and
housing is relatively large and leads to high gas leakage, which is
harmful to turbocharger performance.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention addresses the above needs and achieves
other advantages. A turbocharger in accordance with one embodiment
of the invention comprises a center housing containing a bearing
assembly and a rotary shaft mounted in the bearing assembly, a
compressor wheel affixed to one end of the shaft, and a turbine
wheel affixed to an opposite end of the shaft and disposed in an
axial bore of a turbine housing coupled to an opposite side of the
center housing. The turbine housing defines a chamber surrounding
the turbine wheel for receiving exhaust gas to be directed into the
turbine wheel, and defines a nozzle leading from the chamber to the
turbine wheel. The turbocharger further comprises a sliding piston
assembly disposed in the bore of the turbine housing.
[0008] The piston assembly comprises a tubular piston disposed in
the bore of the turbine housing such that the piston is axially
slidable relative to the turbine housing between a closed position
and an open position, the piston in the closed position
substantially blocking exhaust gas from passing through the nozzle
to the turbine wheel, the piston progressively unblocking the
nozzle as the piston travels toward the open position. The piston
assembly further comprises a tubular carrier inserted axially into
the bore of the turbine housing surrounding the piston and fixed
against axial movement relative to the turbine housing, a radially
outer surface of the carrier engaging an inner surface of the bore
and a radially inner surface of the carrier being slidably engaged
by a radially outer surface of the piston. The carrier defines an
axial split extending a length of the carrier, and the carrier is
resiliently flexible. Accordingly, the axial split allows the
carrier to expand and contract in diameter.
[0009] In accordance with the invention, the carrier's inner
diameter in a relaxed state is only slightly greater than the outer
diameter of the piston such that the gap between them through which
leakage of exhaust gas can occur is a very small. The carrier is
able to adjust to changes in diameter of the turbine housing bore
and piston (which can result from thermal expansion and
contraction) so that the gap between the carrier and piston remains
very small. Furthermore, binding between the piston and carrier can
be avoided because the carrier can expand.
[0010] In one embodiment of the invention, the carrier has a
substantial axial length, preferably approximately equal to that of
the piston. The carrier can include axially elongated apertures
through its side wall, the apertures being circumferentially spaced
about the carrier. The apertures not only reduce the weight of the
carrier, but also provide access to the piston through the carrier
side wall for a piston actuating linkage that connects to the
piston for moving the piston axially in the turbine housing.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0011] Having thus described the invention in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0012] FIG. 1 is a cross-sectional view of a turbocharger in
accordance with one embodiment of the invention, showing the piston
in a closed position;
[0013] FIG. 2 is a view similar to FIG. 1, with the piston in a
partially open position;
[0014] FIG. 3 is a view similar to FIG. 2, showing the piston in a
fully open position;
[0015] FIG. 4 is an isometric view of a turbine assembly in
accordance with one embodiment of the invention; and
[0016] FIG. 5 is an isometric view of the carrier in accordance
with one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present inventions now will be described more fully
hereinafter with reference to the accompanying drawings in which
some but not all embodiments of the inventions are shown. Indeed,
these inventions may be embodied in many different forms and should
not be construed as limited to the embodiments set forth herein;
rather, these embodiments are provided so that this disclosure will
satisfy applicable legal requirements. Like numbers refer to like
elements throughout.
[0018] A turbocharger 20 in accordance with one embodiment of the
invention is shown in FIGS. 1 through 3. The turbocharger includes
a center housing 22 that contains bearings 24 for a rotary shaft 26
of the turbocharger. A compressor housing (not shown) is coupled to
one side of the center housing. A compressor wheel 30 is mounted on
one end of the shaft 26 and is disposed in the compressor housing.
Although not illustrated, it will be understood that the compressor
housing defines an inlet through which air is drawn into the
compressor wheel 30, which compresses the air, and further defines
a diffuser through which the compressed air is discharged from the
compressor wheel into a volute surrounding the compressor wheel.
From the volute, the air is delivered to the intake of an internal
combustion engine (not shown). The turbocharger further comprises a
turbine housing 38 coupled to the opposite side of the center
housing 22. A turbine wheel 40 is mounted on the opposite end of
the shaft 26 from the compressor wheel and is disposed in the
turbine housing. The turbine housing defines a chamber 42 that
surrounds the turbine wheel 40 and receives exhaust gas from the
internal combustion engine. Exhaust gas is directed from the
chamber 42 through a nozzle 43 (FIG. 4) into the turbine wheel 40,
which expands the exhaust gas and is driven thereby so as to drive
the compressor wheel.
[0019] A heat shield 32 is disposed between the center housing 22
and turbine housing 38. The heat shields supports an array of
circumferentially spaced vanes 34 that extend axially from the heat
shield partway across the axial extent of the nozzle 43.
[0020] The turbine housing 38 defines a generally cylindrical bore
44 whose diameter generally corresponds to a radially innermost
extent of the chamber 42. The turbine wheel 40 resides in an
upstream end of the bore 44 and the turbine wheel's rotational axis
is substantially coaxial with the bore. The term "upstream" in this
context refers to the direction of exhaust gas flow through the
bore 44, as the exhaust gas in the chamber 42 flows into the
turbine wheel 40 and is then turned to flow generally axially (left
to right in FIG. 1) through the bore 44 to its downstream end.
[0021] With reference particularly to FIGS. 2 and 3, the
turbocharger includes a sliding piston assembly 50 that resides in
the bore 44 of the turbine housing. The piston assembly comprises a
tubular carrier 52 whose outer diameter is slightly smaller than
the diameter of the turbine housing bore 44 such that the carrier
52 can be slid axially into the bore 44 from its downstream end
(i.e., slid right to left in FIG. 2). The tubular carrier is shown
in isolation in FIG. 5. The bore 44 includes a radially inward step
46 that faces downstream and the carrier includes a radially
outwardly projecting flange or protuberance 54 that abuts the step
46. A retainer clip or ring 56 is snapped into a groove 57 in the
inner surface of the bore 44 behind the carrier 52 to retain the
carrier in the turbine housing. Thus, the carrier is prevented from
moving axially in the bore 44 by the step 46 and the retainer ring
56.
[0022] The piston assembly 50 further comprises a piston 62 of
tubular form. The piston is coaxially disposed within the central
bore of the carrier 52 and is slidable relative to the carrier in
the axial direction. The piston is axially slidable between a
closed position as shown in FIG. 1 wherein the piston abuts the
ends of the vanes 34, an open position as shown in FIG. 3 wherein
the piston is spaced from the vanes by a relatively larger
distance, and various partially open positions therebetween such as
the position shown in FIG. 2 wherein the piston is spaced by
smaller distances from the vanes. In the closed position, the size
of the nozzle through which exhaust gas flows from the chamber 42
to the turbine wheel is a minimum and the exhaust gas is
constrained to flow through the row of vanes 34. In the open
position of the piston, the nozzle flow area is a maximum and part
of the gas flows through the vanes while the remainder flows
through a vaneless annular opening adjacent the vanes.
[0023] The carrier 52 has an axial split 58 (FIG. 5) extending the
length of the carrier. The split enables the carrier to expand and
contract in diameter in response to thermal effects or other
causes. The carrier advantageously has an inner diameter only
slightly greater than the outer diameter of the piston 62, such
that a very small gap exists between the carrier and piston.
Accordingly, leakage flow through the gap is minimized. Because the
carrier can expand and contract in diameter, there is no need to
make the gap large to facilitate assembly or to accommodate
dimensional changes during operation. The ability of the carrier to
expand also means that binding of the piston is avoided.
[0024] The carrier 52 includes a plurality of apertures 60 through
the side wall of the carrier. The apertures are axially elongated
for purposes explained below. The apertures are spaced about the
circumference of the carrier.
[0025] The turbocharger also includes a piston actuating linkage
comprising a fork-shaped swing arm 70. The swing arm has a pair of
arms 72 whose distal ends extend through two of the apertures 60
and engage the piston 62 at diametrically opposite locations of the
piston. The swing arm is disposed adjacent the outer surface of the
carrier and resides in a portion of the bore 44 that has an
enlarged diameter. The swing arm is pivotable about a transverse
axis so as to cause the piston to be advanced axially within the
carrier 52. FIG. 1 shows the piston in the closed position, wherein
the distal ends of the arms 72 are positioned toward one end of the
apertures 60. FIG. 3 shows the piston in the open position in which
the arms are positioned toward the other end of the apertures. The
apertures are axially elongated to allow the requisite degree of
axial travel of the arms 72. The swing arm 70 is actuated by an
actuator mechanism coupled to an actuator such as a vacuum chamber
actuator or the like (not shown).
[0026] The provision of the axially split carrier 52 allows the
carrier to substantially conform to the outer diameter of the
piston at all operating conditions, the carrier expanding or
contracting in diameter along with the piston as temperature
changes. Accordingly, the carrier reduces gas leakage by
maintaining a minimal gap between the carrier and piston. Although
some gas leakage can occur through the axial split when it opens
up, but it is expected this leakage would be small. Gas leakage
between the carrier and the turbine housing is minimized by the
engagement between the lip or projection 54 and the corresponding
step surface 46 of the turbine housing, and by the snap ring 56
that presses the projection 54 against the surface 46.
[0027] Many modifications and other embodiments of the inventions
set forth herein will come to mind to one skilled in the art to
which these inventions pertain having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. Therefore, it is to be understood that the inventions are
not to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *